1. Field of the Invention
The present invention relates in general to conductive polymeric nanocomposites. More particularly, it relates to a method for producing conductive polyaniline/layered inorganic nanocomposites.
2. Description of the Related Arts
Nanocomposites are a new class of materials which exhibit ultrafine phase dimensions, typically in the range 1-100 nm. Experimental work on these materials has generally shown that virtually all types and classes of nanocomposites lead to new and improved properties such as increased stiffness, strength, and heat resistance, and decreased moisture absorption, flammability, and permeability, when compared to their micro- and macrocomposite counterparts.
In the past decade, conducting polymers have been used in many fields, such as batteries, displays, optics, EMI shielding, LEDs, sensors, and the aeronautical industry. High molecular weight polyaniline has emerged as one of the more promising conducting polymers because of its excellent chemical stability combined with respectable levels of electrical conductivity of the doped or protonated material. Processing of polyaniline high polymers into useful objects and devices, however, has been problematic. Melt processing is not possible, since the polymer decomposes at temperatures below a softening or melting point. In addition, major difficulties have been encountered in attempts to dissolve the high molecular weight polymer.
One known method to improve the processibility of polyaniline is by employing a protonic acid dopant containing a long-chain sulfonic group in the polymerization of aniline to form an emulsified colloidal dispersion. However, this method requires a large quantity of long-chain dopants, which decrease the conductivity and mechanical properties of polyaniline. In addition, high aspect ratios of polyaniline are unavailable through this method.
In conventional guest-host methods for preparing polyaniline/layered inorganic composites, aniline monomers are interposed between layered hosts, and then subjected to oxidative polymerization to form composites with highly ordered polymer matrices. The polyaniline composite thus obtained, however, commonly has a conductivity lower than 10.sup.-2 S/cm. Moreover, they do not give nanoscale structures. The interlayer spacing (d-spacing) of the inorganic layers is less than 15 .ANG..
The aim of this present invention is to provide a conductive polyaniline nanocomposite which has a conductivity of greater than 10.sup.-1 S/cm.